Timeline for Precision of LinearModelFit with Polynomials
Current License: CC BY-SA 3.0
11 events
| when toggle format | what | by | license | comment | |
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| Jun 11, 2015 at 8:51 | vote | accept | mcocdawc | ||
| Jun 11, 2015 at 8:51 | vote | accept | mcocdawc | ||
| Jun 11, 2015 at 8:51 | |||||
| Jun 10, 2015 at 21:40 | answer | added | JimB | timeline score: 4 | |
| Jun 10, 2015 at 19:46 | comment | added | mcocdawc | I got the same problem whit the 6.39247197093749 when i copied from the website. It works if it is read from a CSV file. | |
| Jun 10, 2015 at 19:43 | history | edited | mcocdawc | CC BY-SA 3.0 |
added 242 characters in body
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| Jun 10, 2015 at 19:26 | comment | added | MarcoB |
Unfortunately I can't help you in pinpointing the origin of the drop in precision, but it seems that you can get what you want by manually setting your input values to an arbitrary (high) precision: tableofvalues = SetPrecision[#, 40]& @ {yourdata}. You will then obtain coefficients from your expression that are numerically the same to within the precision you have set. Further note: I also get the 6.39... answers from your code that @belisarius reported.
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| Jun 10, 2015 at 19:15 | comment | added | Dr. belisarius |
Using your data, the results from your NumberForm[ ] in my machine are more like 6.39247197093749 ....
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| Jun 10, 2015 at 19:09 | comment | added | mcocdawc | Beside from this I would like to understand where this decrease of precision of 8 orders of magnitude comes from. | |
| Jun 10, 2015 at 19:08 | comment | added | mcocdawc | I made this table as minimal example. But I also need coupling constants lateron. For example the linear factor a*x[1]*x[4]. So it's not possible to just skipt x[3] and x[4] and mirror x[1] and x[2] onto them. For the diagonal elements this was of course possible. | |
| Jun 10, 2015 at 18:36 | comment | added | Dr. belisarius | Just curious: Adding degrees of freedom artificially will make your results worse. If you already know that the model's coefficients have a certain relationship, why don't you state that right in the model? | |
| Jun 10, 2015 at 18:16 | history | asked | mcocdawc | CC BY-SA 3.0 |